Crystal structure of Au-pseudocarbyne(C₆)

Carbyne-related materials permit exploring the potentially extraordinary properties of this long-sought but still elusive carbon allotrope. However, accurate understanding of these materials is challenging. Here we report the crystal structure of a Au-pseudocarbyne, a representative of a possible new family of materials consisting of sp-hybridized carbon chains and stabilizing metal atoms. Au-pseudocarbyne(C₆), the representative pseudocarbyne containing six-membered carbon chains, has space group P6/mmm¹⁹¹ and unit-cell parameters a = b = 0.60 nm, c = 0.896 nm, α = β = 90°, γ = 120°. Its long-range structure can be understood as intimately intergrown bundles, each consisting of six parallel, infinite carbon chains surrounding a column of gold atoms. This compound, together with its eight-membered counterpart Au-pseudocarbyne(C₈), shows that interesting new materials resembling the carbyne structure and sharing some of its properties can be designed and developed. The current work raises serious questions regarding recent reports of carbyne synthesis.